136 Rev. W. D. Conybeare on a Geological Map of [Feb. 



occur; and in the opinion of many geologists favour the hypo- 

 thesis of their ignigenous formation. 



All these formations are shown in their constant and regular 

 order of succession in the greater part of the English and Irish 

 coal fields ; and the only Scotch coal field of which we have 

 any distinct account (that of Clackmannan), entirely harmonises. 

 The structure of the carboniferous districts of the" Netherlands, 

 and (if we may judge from Beudant's description), of Hungary 

 also, is exactly parallel. In some instances, however, the third 

 and fourth systems being deficient, the coal measures repose 

 immediately on the transition limestones, slates, &c. (as in Cole- 

 broke Dale, and Dudley, in England ; in the Hartz, and many 

 places on the Continent. 



The order of superposition, however, is never inverted, nor 

 is there, one single instance on record in which any workable seam 

 of coal has been found below the. third or fourth system above 

 enumerated, unless we consider the anthracite sometimes asso- 

 ciated with transition slates, and which may be readily distin- 

 guished from the true coal formation, as an exception. 



The limestones of the third series, and the conglomerates and 

 sandstones of the fourth, are generally referred by continental 

 geologists to the transition class. (See Von Raumer on the 

 Slate Mountains of the Netherlands, &c. Daubuisson, Geologie; 

 Beudaut, Hongrie ; Humboldt, &c). The representations of 

 every one of the above writers render it absolutely impossible 

 to confound the rothetodteliegende of Germany with the conglo- 

 merates of the fourth system above described. 



I have, in another work, assigned my reasons at length for 

 constituting a separate order to include the whole of these four 

 systems rather than referring any part of them to the transition 

 class with which, however, they are very nearly allied. 



The geologists of the Continent very commonly consider the 

 rothelodteliegende (a formation immediately overlying the coal 

 measures), as forming part of this series. 



I prefer the view entertained by Prof. Buckland, who has, in 

 rspeated journeys in the north of Germany, minutely examined the 

 relations of the rotheliegende with reference to this question, and 

 ■who considers it as the lowest member of the great sandstoneseries 

 forming the next natural group above the carboniferous series. 

 Though conscious how little weight my own evidence will add to 

 this high authority, I may brieflystate thatmy ownpersonalexami- 

 nation of the Thuringerwald led me to the same conclusion. I 

 have only at present to repeat my assertion, that Lehman, Freis- 

 leben,* Von Buch, Von rvaumer, Karsten, Keferstein, Daubuis- 



* Although I purposely avoid entering into details at present, I shall subjoin one 

 extract from Freisleben, which is entirely decisive. He observes that some geologists 

 are inclined to consider the coal rocks and the rotheliegende as subordinate members of 

 one great formation ; but opposes his own view of the subject to theirs, stating that he 

 considers them " als zwey einander zwar ganz nahe stehende, abcr dennoch von cinandcr 



